LAWN-BOY V-ENGINE SERVICE MANUAL Table of Contents – Page 1 of 2 REFERENCE SECTION SAFETY SPECIFICATIONS - ENGINE SPECIFICATIONS SPECIFICATIONS - ENGINE FASTENER TORQUE REQUIREMENTS SPECIFICATIONS - CARBURETOR SPECIFICATIONS (WALBRO LMR-16) SPECIAL TOOL REQUIREMENTS TROUBLESHOOTING MAINTENANCE SECTION 1 WALBRO LMR-16 CARBURETOR LMR-16 CARBURETOR - IDENTIFICATION LMR-16 CARBURETOR - THEORY OF OPERATION LMR-16 CARBURETOR - GOVERNOR THEORY LMR-16 CARBURETOR - REMOVAL LMR-16 CARBURETOR - DISASSEMBLY LMR-16 CARB
LAWN-BOY V-ENGINE SERVICE MANUAL Table of Contents – Page 2 of 2 SECTION 3 FUEL SYSTEM FUEL SYSTEM - OPERATION FUEL SYSTEM - CAP SERVICE FUEL SYSTEM - TANK REMOVAL FUEL SYSTEM - CLEANING FUEL SYSTEM - TANK INSTALLATION SECTION 4 IGNITION SYSTEM IGNITION SYSTEM - TROUBLESHOOTING IGNITION SYSTEM - SPARK PLUG OPERATION IGNITION SYSTEM - SPARK PLUG SERVICE IGNITION SYSTEM - CD PACK OPERATION IGNITION SYSTEM - CD PACK AIR GAP ADJUSTMENT IGNITION SYSTEM - CD PACK REMOVAL/INSTALLATION IGNITION SYSTEM - FLYWHEEL OP
V-Engine
TABLE OF CONTENTS Reference Section Safety Information 9 Engine Specifications 10 Engine Fastener Torque Requirements 11 Carburetor Specifications 12 Special Tool Requirements 13 Troubleshooting 14 Maintenance 19 Recommended Maintenance Schedule 19 Air Filter 19 Spark Plug 20 Cleaning the Exhaust System 21 Service Section Section 1 LMR-16 Carburetor Identification 25 Theory of Operation 25 Governor Theory 25 Removal 26 Disassembly 27 Cleaning and Inspection 27 Assembly 28 Presetting the Gover
TABLE OF CONTENTS Service Section (cont'd) Section 2 Primer Start Carburetor Identification 32 Theory of Operation 32 Governor The0ry 32 Removal 33 Disassembly 34 Cleaning and Inspection 34 Assembly 34 Installation 35 Presetting the Governor 35 Final Check 35 Servicing the Air Filter 36 Troubleshooting 36 Section 3 Fuel System Operation 37 Cap Service 37 Tank Removal 38 Section 4 Cleaning 38 Tank installation 38 Ignition System Troubleshooting 39 Spark Plug Operation 39 Service 39
TABLE OF CONTENTS ServiceSection(cont’d) Section 4 (cont’d) CD Pack Operation 40 Air Gap Adjustment 41 Removal Installation 41 Flywheel Operation 41 Removal 41 Installation Section 5 42 Rewind Starter Operation 43 Removal and Disassembly 43 Reassembly 44 Section 6 Engine Description ......................................................... Theory of Operation ............................................................................................ Service Tips....................................
TABLE OF CONTENTS Service Section (cont’d) Section 7 Pivoting Zone Start Brake Introduction 53 Operation 53 Disassembly 53 Assembly 54 Appendix A Exploded View Diagrams A-1 Table of Contents 6 V-Engine
SAFETY INFORMATION ThissafetysymbolmeansWARNINGorPERSONALSAFETYINSTRUCTIONreadtheinstruction because it has to do with your safety. Failure to comply with the instruction may result in personal injury or even death. This manual is intended as a service and repair manual only. The safety instructions provided herein are for troubleshooting, service and repair of the engine only. The individual Operator’s manual will contain safety information on the complete product powered by theV engine.
Engine Specifications 2.3810 Bore 2.3800 mm) (60.477 85.852 1.7497” 1.7520 (44.501 mm) 44.442 Stroke Connecting length rod 3.00 (76.2 mm) Wrist pin diameter Wrist pin offset .5000”(12.7 mm) .070 (1.78 mm) toward major thrust side Crankpin diameter .742” (18.85 mm) Top and bottom main bearings Dia: Top: .875” (22.23 mm) Bottom:1.125” (28.58 mm) Displacement 7.78 cu in (127.51 cc) Horsepower 4.5 Compression ratio 5.91:l (Range 5.
SPECIFICATIONS (cont'd) Engine Fastener Torque Requirements Torque 45 375 50 ft Ibs (60 67 425in lbs (42 5 7 in Ibs (.5 N-m) 47 .8 N-m) N-m) 70 in Ibs (6.7 7.8 N-m) 45 55 in Ibs (5.0 6.1 N-m) 110in Ibs (10 12 N-m) 60 90 - 105 115in Ibs (12 13 N-m) 300 350 in Ibs (34 39 N-m) _ _ I _ - - - - - ~ 15 25in Ibs (1.7 2.8 N-m) 150 190in Ibs (17 22 N-m) 140 200in Ibs (16 22 N-m) 10 13in Ibs (1.1 1.5 65 75 in Ibs (7.3 8.4 N-m) 58 70 in Ibs (6.5 7.
SPECIFICATIONS (cont’d) Carburetor Specifications (Walbro LMR-16) Carburetor Specifications (Primer Start) 12 Reference Section
SPECIAL TOOL REQUIREMENTS V-Engine Tool Requirements DESCRIPTION V Engine Tool 612490 Kit Includes 604659 Gauge Gap Air tools shown to service V below Engine. necessary Sets .010” gap between flywheel and coil. 03 21 61Stop Piston Prevents piston from traveling over TDC. Use when servicing flywheel or installing piston. __- Crankshaft 609968 Gauge Sets correct gap on crankshaft support. Piston Ring Compressor 609967 Compressesringsintopistongroovesduringinstallationofpiston.
TROUBLESHOOTING Contents Engine Will Not Start When“Cold 14 Engine Will Start When“Cold But Not When “Hot” ......................................................
TROUBLESHOOTING (cont’d) Engine Will Start When “Cold”, But Not When “Hot” e Flooded With Fuel” table Engine Will Not Produce Spark Possible Causes I Coil kill wiregrounded Locateandeliminatetheunwantedground - - - ~ - - Engine Flooded With Fuel I Remedies Causes Possible Overuse of “choke” position(‘93 units only) Take throttle off “choke” position I stsadjusted cable Throttle Air cleaner plugged Wash and re-oil air cleaner element Fouled spark plug Replace spark plug I carburetor, Clean pa
TROUBLESHOOTING ‘(cont’d) Engine Surges Possible Causes Remedies Fouled idle circuit (‘93 models only) Clean idle circuit Air leak Check sealing surfaces,oil seals, gaskets, and Restricted fuel flow Check filters and fuel line Engine Backfires I edies Causes Possible Flywheel key sheared Replace key Muffler filled with carbon Clean muffler Exhaust ports plugged Clean ports Engine Overheats Possible Causes Remedies Cylinder head cooling fins clogged Clean fins thoroughly Restricted main
s s es y s TROUBLESHOOTING (cont’d) Engine Crankshaft Will Not Turn I Possible Engine brake incorrectly engaged Disengage brake and inspect and repair as necessary Blade jammed in housing Inspect and repair or replace Pistonseized in itscylinder Inspect and repair or replace Starter jammed Repair starter Engine Produces Mechanical Knocking Sound I Possible Engine Pre-Ignites Possible Wrong spark Install plug hot too correct the spark type of plug Replace with fresh unleaded regular fuel _D
Engine Stalls Spark Plug Fouled fuel Use of leaded
Recommeded Maintenance Schedule Check blade and engine mountingf bolts and screws tight to ensure safe operation. 25 Hours Air Filter 50 Hours Blade Brake replace. I I Exhaust Ports Check for leakage and/ordee to riraoitn I 100 Hours Cooling System Air Filter Once every season, or every 25 hours, clean the air filter housing and element. Do so more frequently under dusty conditions. Filter Notes: Do not operate the engine without theair filter in place.
MAINTENANCE (cont’d) Air Filter (cont’d) Spark Plug 2. Washairfilter in laundrydetergent. A spark plug that is dirty, pitted, carbon coveredor has worn electrodes may cause hard starting and poor operation. Squeeze filter to remove excess liquid and blot dry with a paper towel or rag (Figure 2). Clean or replace spark plug once a season or every 25 hours, whichever occurs first. Use Champion RJ12C, or equivalent. Remove spark plug and clean with a wire brush, removing carbon buildup. DO NOT SANDBLAST.
MAINTENANCE (cont'd) Cleaning The Exhaust System 4. Remove the three bolts to remove the muffler cover. Drop the cover down to inspect the condition of the exhaust ports, etc. (Figure 8). 5. Pull the starter rope until the piston covers the exhaust ports (Figure 9). Clean them with a 3/8” (9 mm) wooden dowel. Warning: Disconnect the spark plug wireto prevent accidentally starting the engine. 1.
SECTION 1 WALBRO LMR-16 CARBURETOR LMR-16 Carburetor Identification LMR-16 Carburetor Governor Theory The LMR-16 carburetor canbe identified by its aluminum body. Walbro (the manufacturer's name)is also stamped on the side of the body. These carburetor's were used on 1993 models. The shaft of the governor air vaneis attached to the throttle disc of the carburetorso that air flow, created by the rotating flywheel, attemptsto close the throttle.
LMR-16 Carburetor Removal 1. Disconnect spark plug wire. 2. Remove Fuel Tank (See page 38). 3. Open and remove air cleaner cover and air filter element. 4. Detach carburetor from engine by removingtwo mounting bolts. Remove and discard the two small carburetor gaskets. Save the carburetor heat shield. 5. Disconnect the fuel line. 6. Pull the carburetor assembly down and away from the engine such that the air vane clears the hole in the shroud base (Figure 13). 7.
LMR-16 Carburetor Disassembly Remove the idle adjustment needle and spring. .l. Remove the in-line filter from the fuel inlet. Remove the bowl retaining bolt and gasket, the bowl and the bowl gasket. 2. Remove the screw holding the air vane to the throttle shaft. Remove the air vane collar and governor spring and remove the throttle valve screw, plate and shaft(Figure 15). Remove the float shaft, float and inlet needle.
LMR-16 Carburetor Assembly 5. 1. Install Welch plug using a blunt tool having the same diameter as the Welch plug. 2. Install the fuel inlet valve seat: coat the seat with oil and install it grooved side down(Figure 18). Place bowl onto the carburetor body and install (Figure 20). the bowl retaining bolt and gasket n INSTALL Figure 20 Install idle needle and spring. Turn in until the needle seats lightly then back it out5/8 3/4 of a turn. Install the choke shaft and spring as shown (Figure 21).
LMR-16 Carburetor Assembly (cont’d) 10. Place a drop of LMR-16 Carburetor Presetting the Governor Loctite on the screw and install thethrottleshaftandvalvewiththevalvehole the left (Figure 23). to 1. Hold the carburetor with the mounting flange facing you and the throttle wide open. 2. Preset the governor by turning the collar so that the window on the collar is3-4 clicks to the right of the pulse hole. LMR-16 Carburetor Assembling Air Box to Carburetor 1.
LMR-16 Carburetor Assembly (cont’d) LMR-16 Carburetory Choke Adjustment 6. 1.Movethrottlecontrol 7. Installtheremainingcarburetorgasket;make sure all pulse holes are aligned. Hook the control cable into the control lever and fasten the cableto the air box. LMR-16 Carburetor Installation 1. While holding the carburetor and parts together, turn the assembly and guide the air vane into the opening in the shroud base (Figure 13). 2.Installtheboltsfingertight. 3.
LMR-16 CARBURETOR-TROUBLESHOOTING Engine Starts Hard Engine Runs Rich Dirty air cleaner I Clean or replace air filter element I carburetor Clean Dirt in carburetor Engine Runs Lean Carburetor bolts tight Tighten not 55 45 bolts to I Improper carburetor adjustment in(5.1 Ibs I 6.
SECTION 2 PRIMER START CARBURETOR Primer Start Carburetor Identification The primer start carburetoris easily identified byits primer and its black plastic body.It is different from earlier Lawn-Boy plastic body carburetors because it does not have the adjustable needle behind the airvane governor. This carburetoris found on 1994 and newer V-Engines. Byinsertingatubefromthecarburetorfloatbowlinto the venturi (Figure 30), lower air pressure at the venturi draws fuel through the tube.
Primer Start Carburetor Removal 1. Disconnectsparkplugwire. 2. Removefuellineanddrain;removethefueltank (see page 38). 3. Open and remove air cleaner cover and air filter element. Remove the two plastic plugs covering the mounting screws. 4. Detachcarburetorfromenginebyremovingtwo mounting screws. Discard thetwo smaller carburetor gaskets on either sideof the carburetor shield. Keep the heat shield for later installation. 5.
Primer Start Carburetor Dissassembly 1. At the throat of the carburetor, using a needle nose pliers, gently pull the throttle plate out of the air vane assembly shaft (Figure 35). Notice the orientation of the small protrusions on the throttle plate as you pull it out. The single protrusion should be on your left; next to the hole at the 9 o’clock position). Remove the fuel filter from the fuel nozzle. Remove the float hinge pin, the inlet valve needle assembly (withits clip) and the float (Figure 36).
Primer Start Carburetor Assembly (cont’d) 8. Install a new fuel bowl gasket and the fuel bowl with the four bowl retaining screws. 9. Hook the governor spring into the bottom of the governor collar. 1. Turn the collar clockwise to increase spring tension (and engine RPMs) or counterclockwise to decrease spring tension and RPMs (Figure 37). Preset the governor collar 3 or 4 clicks clockwise. 10. Holding the spring in the collar, hook the other end of the spring into the speed control arm.
Primer Start Carburetor Servicing the Air Filter 1. To remove the air filter, at the left side unsnap the wire holder from the cover, and then unsnap the cover from the clear plastic shell. Remove the cover andair filter element (Figure 38). 2. Clean and re-oil the air filter element according to the procedure in Maintenance, pages 19 and 20. CAUTION: Do not operate the engine without a filter element or with a dry element; engine life will be shortened.
FUEL SYSTEM Fuel System Operation Fuel System Cap Service The V Engine uses a 1.5 quart plastic fuel tank (Figure 39) with a non-replaceable75 micron in-tank filter screen. The filter is chemically welded in the bottom of the tank over a sediment reservoir. The tank is mounted above thelevel of the carburetor and uses gravity to supply fuel through a .25”I.D. (6.35 mm) rubber hose to the carburetor. Thefuel hose is friction-fitted to the tank outlet at one end and to the carburetor at the other end. 1.
Fuel System Tank Removal 1. 3. Disassemblethestarterrope “T” handle (Figure 41) sufficiently to untie 42) (or cut) the starter rope knot and release the rope. (The plastic rope stop prevents the rope from rewinding completing into the starter).
SECTION 4 IGNITIONSYSTEM Ignition System Troubleshooting Check the ignition systemin the following order: Spark plug (connection & wire, condition) CD Pack (air gap, connections or spark) Flywheel (key and magnets) Use the following table to aidin diagnosing the problem.
Ignition System CD Pack Operation When the SCR is triggered or “fires”, upto 200 volts DC, stored in the capacitor, travels to the spark coil. Here it is stepped up to as much as25,000 volts and is discharged across the electrodes of the spark plug (Figure 46). The V Engine uses a solid state ignition module to generate an electrical pulse for the spark plug.
Ignition System CD Pack Air Gap Adjustment 1. Rotateflywheeluntilthemagnetsaredirectly adjacent to theCD Pack as shown in Figure 49. Ignition System Flywheel Operation The flywheel is connected directlyto the Crankshaft (secured by a flywheel key and nut) and turns at the same speed as the crankshaft. Two permanent magnets, imbedded in the flywheel, rotate past the coil in the CD Pack to begin the generationof electricity.
2.Removeshroudandfuelhoses. 4. Torque flywheel nut Ibs (43 47 N-m) 3. Remove flywheel nut. (Figure 54) to 375-425 in 4.Removeflywheelby pulling uponedge of flywheel while striking wide fin of flywheel with a soft hammer (Figure 52). Figure 54 Figure 52 5.Removekeyandcheck its condition. 6. Replacecrankshaftand/orflywheel if keyway is distorted or cracked. 7. Check flywheel for wear and flywheel magnets for strength. Ignition System Flywheel Installation 1.
SECTION 5 REWIND STARTER RewindStarterOperation The rewind starter operates through a retainer/friction disc that causestwo engagement dogsto extend from the center of the rewind starter and engage the inside of the starter hub on the flywheel. The engagement dogs move into contact with the starter hub when the rewind rope is pulled.
Rewind Starter Reassembly 1. Lubricate the center post of the rewind starter with a small amountof general purpose grease. 2. Place the reel assembly on the center post of the rewind starter and turn the reel counterclockwise until the hook on the reel spring engages the spring retainer on the center postof the starter. (Figure 57). 4. Install theretainingplateandPhillipsshoulder screw. Tighten the screw to a torque of 33 in Ibs (3.7 N-m) (Figure 59).
Rewind Starter Reassembly (cont'd) 7. Reattach the shroud to the shroud base with four screws. Be sure the3/8 screw (3/8” head, 1/4" Dia) is installed at the frontof the shroud. Tighten all screws to a torqueof 58 70 in Ibs (6.6 7.9 N-m) (Figure 61) 8. Turn the fuel tank over and notice the two extruded tabs. These tabs match the holes in the rear portion of the shroud and will automatically align the mounting holesof the fuel tank and shroud when the fuel tankis inserted correctly. 9.
SECTION 6 Engine Description Themovement of the piston towardsthesparkplug also has an important effect in the crankcase. Once the transfer port is sealed, the crankcase is under vacuum. This action pulls the reed valve open and draws in a fresh charge of air/fuel mixture. Two-cycle engines have special advantages which make their use more practicalin certain applications. Two cycle engines are lightweight with an excellent power-to-weight ratio and can be operatedin any position.
Engine Service Tips 7. Carburetor A-4). page Gaskets (24, Carburetor gaskets (24)on either side of the carburetor shield (1)may be leaking or damaged causing air leaks into the engine (may cause power fluctuations). Ensure that air Halves (21, page A-2). cleaner/carburetormounting screws (6) are 1. Cylinder/Crankcase of 45 55 inIbs (5.0 6.1 The two halvesareamatchedpairandcannottightenedtoatorque mixed.
Engine Removal (cont’d) 5. Removebrakeplateassembly by removingone 10 mm shoulder screw and one3 / 8 washerhead screw. Place the assembly on the mower deck and disconnect the ground wire (that goes to the CD Pack). (Figure 66). Figure 66 7. RemovetheCDPack(page41). Note: Step 8 covers ‘93 carburetors; ‘94 carburetors have an additional wire holder that must be released to remove theair cleaner element. Mounting screws are identical. 8.
Engine Removal (cont’d) 2. 10. Remove the spark plug and install piston stop Removetheentirecrankshaftassemblyand discard the oil seals (3, page A-2). 3.Carefullyremovethe HSH (hex,sockethead)cap screws (9,page A-2) to remove the connecting rod cap and the split bearing liner. The needle roller bearings are under the split bearing liner (Figure 70). (p/n 677389) in the spark plug hole. 1 1. Remove the 15/16 blade nut that secures the blade and mulch fan to the engine shaft.
Engine Inspection and Repair Check bearings for wear and freedom of movement: replace if questionable. Check rings for sticking, remove and check rings for wear or damage; replace ringsif questionable. Engine Reed Valve Service These assemblies (Figure 73) permit fuel mixturesto enter the crankcaseon compression strokes andto trap fuel mixturesin the crankcase on power strokes. Check all parts for wear or damage and replace if questionable.
Engine Reassembly 1. 6. Oil Securewrist pin usingsnapring.Makesure squareedge of snapringfacesoutandring opening faces up (toward topof piston) (Figure 75). parts and use piston stop (p/n 677389) and ring’compressor(p/n 609967) to install piston with “BTM” mark facing down toward exhaust ports (Figure 77). Note: Letters “BTM” were omitted on some engines. However, the small “rectangle” should still be visible through ports. SNAP RING Figure 75 2.
8. Carefully align the two crankcase halves using the alignment pin and its matching hole; press the two halves together (Figure 79). Reinstalling External Components 10. Reattach the flywheel brake system. 11.Install new oil seals. 12.Installshroudbase. 13. Clean crankshaft and flywheel hub and install flywheel (see page 42). 14. Installcarburetor and governor assembly (see page 30 for '93 models, page 35 for '94 models). 15. Install starter and shroud assembly and starter handle (see page 45). 16.
Section Introduction The switch is closed when the blade control bail is in the “at rest” (vertical) position (Figure 81). Lowering the bail to the main mower handle opens the switch. In 1982 the federal government mandated that all consumer walk behind mowers with a cut 25” of (63.5 cm) or less be equipped with safety devices. There are two primary criteria which these devices must meet: 1. Switch leads are connected to the primary side of the coil and to ground.
Pivoting Zone Start Brake Disassembly (cont'd) Note: Numbers in parentheses in the following procedures refer to Figure 82 on previous page. 2. Securethereplacementbrakeplate to the engine with shoulder screw (7). Tighten it to 90 in Ibs (9.2 N-m) Ensure that the brake plate pivots freely. 3. If the engine and blade are taking more than 3 seconds to stop when the blade control bailis released , inspect the brake pad for excessive wear and replace if necessary.
This appendix containsan assortment of diagrams which may help youin the service and repairof the V Engine of this section They are listed below as they appear on the following pages Power Head Exploded View A-2 Ignition and Exhaust Exploded View A-3 Starter and Walbro LMR-16 Carburetor Exploded View A-4 Walbro LMR-16 Carburetor Assembly Exploded View A-5 Primer Start Carburetor Assembly Exploded View A-6 Service Section A-1 Appendix
Power Head Exploded View @-3 9 1 Core plug (4) 2 Dowel 3 Oil Seal (2) 4 Needle bearing 5 Slotted head screw (2) 6 Reed backup plate 7 Carburetor reed 8 Washer head hex screw (4) 9 HSH cap screw (2) 10 Split liner (2) 11 Needle Bearings 12 Upper main bearing 13 Crankshaft Appendix 14 Bearing 15 Connecting rod assembly 16 Retaining ring 17 Wrist pin 18 Piston 19 Piston ring 20 Top piston ring 21 Cylinder and crankcase assembly 22 Sealant (not illustrated) A-2 Service Section
Ignition and Exhaust Exploded View -3 1 Baffle 2 Screw (4) 3 Muffler plate 4 Ground strap stop 5 Self-tapping screw 6 Brake switch leadwire 7 Ground strap 8 Insulation strap 9 Self-expanding plastic rivet (2) 10 Shoulder screw 11 Brake plate assembly 12 Screw 13 Brake mounting plate 14 Hex washer-head screw 15 CD ignition pack 16 Spark plug 17 Exhaust gasket 18 Muffler cover 19 Screw (3) Service
Starter and Walbro LMR-16 Carburetor Exploded View 1 Carburetor heat shield 2 Gasket 3 Carburetor assembly 4 Air filter base 5 (not used) 6 Screw (2) 7 Air filter 8 Air filter cover 9 Retainer 10 Lever 11 Screw 12 Washer 13 Throttle spring Appendix 14 Air vane collar 15 Air vane 16 Screw (3) 17 Shroud assembly 18 Hex flange nut (4) 19 Nut 20 Starter hub 21 Flywheel assembly 22 Shroud base 23 Key 24 Carburetor gasket 25 Lockwasher A-4 Section Service
Walbro LMR-16 Carburetor Exploded View 12 13 14 !I 15 16 17 1 Ref Part No. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Description Valve inlet needle Valve seat Choke valve Choke return spring Idle needle spring Welch plug Idle needle Choke shaft Throttle shaft Throttle valve Throttle valve screw Float Float shaft Bowl gasket Fuel bowl Bowl retainer gasket Bowl screw Ref Part Quantity Quantity No. No.
Primer Start Carburetor Assembly Exploded View 6 9 10 11 12 21 17 18 19 -Air vane 2 Retainer 3 Lever 4 Air vane collar 5 Throttle spring 6 Throttle plate 7 Cable bracket 8 Screw (2) 9 Air filter base 10 Inlet seat 11 Inlet needle 12 Retainer 13 Gasket 14 Main nozzle 15 Filter screen 16 Float 17 Float pin 18 Carburetor bowl 19 Screw (4) 20 Washer 21 Main jet 22 Air filter 23 Air filter cover 24 Air filter cover retainer Service Section
